''small intestine is the site of the complete digestion of carbohydrates ,fats and proteins".Explain how it performs that function..

When the partly digested food reaches the small intestine, the juices secreted by the small intestine complete the process of digestion. The secreted juices in the small intestines consists of maltase, sucrase, lactase, peptidase and lipase.

Digestion in Small Intestine

The digestion of food takes place in duodenum, which is the first part of small intestine.

The small intestine receives digestive juices from liver (bile juice) and pancreas (pancreatic juice). Small intestine itself also secretes digestive juices.

The bile juice is secreted by the liver. It does not contain any enzyme, but still is essential for digestion since it breaks the fats into smaller droplets so that the enzymes could act on them efficiently.

Three of the major enzymes present in the pancreatic juice are − trypsin, amylase and lipase.

Action of pancreatic juice results in:

After being partially digested, the food moves to the second part of small intestine where it is acted upon by enzymes such as maltase, sucrase, and lactase.

Action of intestinal juice results in:

What is the function of the liver in the digestive system? The liver is the largest gland of the body. It is a reddish-brown gland situated on the right side of the upper part of the abdomen. The main function of the liver is to secrete bile juice. Bile juice is stored in a sac-like structure called the gall bladder.

What is the function of bile? Bile takes part in the digestion of fats present in the ingested food.

What is the pancreas? Does it perform the same function as the liver?

The pancreas is a large cream-coloured gland. It is situated just below the stomach. It secretes pancreatic juice, which consists of protease, amylase and lipase enzymes. These juices take part in the digestion of carbohydrates, lipids and proteins by breaking them into simpler substances for example, amylase breaks starch into maltose, while lipase breaks complex fats into simple fats.


Hence, it is the small intestine where

  • carbohydrates are broken down into simple sugar such as glucose
  • fats are broken down into fatty acids and glycerol
  • proteins are broken down into amino acids

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